Excretion: Important Questions

Excretion

Evaluation

1. Arrange the following structures in the order that a drop of water entering the nephron would encounter them.

a. Afferent arteriole

b. Bowman’s capsule

c. Collecting duct

d. Distal tubule

e. Glomerulus

f. Loop of Henle

g. Proximal tubule

h. Renal pelvis

Answer:

a. Afferent arteriole

e. Glomerulus

b. Bowman’s capsule

g. Proximal tubule

f. Loop of Henle

d. Distal tubule

c. Collecting duct

h. Renal pelvis

2. Name the three filtration barriers that solutes must come across as they move from plasma to the lumen of Bowman’s capsule. What components of the blood are usually excluded by these layers?

3. What forces promote glomerular filtration? What forces opposes them? What is meant by net filtration pressure?

4. Identify the following structures and explain their significance in renal physiology?

a. Juxtaglomerular apparatus

b. Podocytes

c. Sphincters in the bladder

d. Renal cortex

5. In which segment of the nephron most of the re-absorption of substances takes place?

6. When a molecule or ion is reabsorbed from the lumen of the nephron, where does it go? If a solute is filtered and not reabsorbed from the tubule, where does it go?

7. Match each of the following substances with its mode of transportation in proximal tubular reabsorption.

a. Na¹ - simple diffusion

b. Glucose - primary active transport

c. Urea - indirect active transport

d. Plasma - paracellular movement

e. proteins - facilitated diffusion

f. Water - endocytosis

8. Which segment is the site of secretion and regulated reabsorption of ions and pH homeostasis?

9. What solute is normally present in the body to estimate GFR in humans?

10. Which part of the autonomic nervous system is involved in micturation process?

11. Match the following terms.

a. α-receptor arteriole - afferent

b. Autoregulation - basal lamina

c. Bowman’s capsule - capillary blood pressure

d. Capsule fluid pressure - colloid osmotic pressure

e. Glomerulus - GFR

f. Podocyte - JG cells

g. Vasoconstriction - plasma proteins Norepinepherine

12. If the afferent arteriole of the nephron constricts, what happens to the GFR in that nephron? If the efferent arteriole constricts what happens to the GFR in that nephron? Assume that no auto regulation takes place.

13. How is the process of micturition altered by toilet training?

14. Concentration of urine depends upon which part of the nephron

a. Bowman’s capsule

b. length of Henle’s loop

c. P.C.T.

d. net work of capillaries arising from glomerulus

15. If Henle’s loop were absent from mammalian nephron, which one of the following is to be expected?

a. There will be no urine formation

b. There will be hardly any change in the quality and quantity of urine formed

c. The urine will be more concentrated

d. The urine will be more dilute

16. A person who is on a long hunger strike and is surviving only on water, will have

a. Less amino acids in his urine

b. Macula densa cells

c. Less urea in his urine

d. More sodium in his urine

17. What will happen if the stretch receptors of the urinary bladder wall are totally removed?

a. Micturition will continue

b. Urine will be continue to collect normally in the bladder

c. there will be micturition

d. urine will not collection the bladder

18.  The end product of Ornithine cycle is

a. carbon dioxide

b. uric acid

c. urea

d. ammonia

19. Identify the wrong match

a. Bowman’s capsule - Glomerular filteration

b. DCT - Absorption of glucose

c. Henle’s loop - Concentration of urine

d. PCT - Absorption of Na¹ and K¹ ions

20. Podocytes are the cells present on the

a. Outer wall of Bowman’s capsule

b. Inner wall of Bowman’s capsule

c. neck of nephron

d. Wall glomerular capillaries

21. Glomerular filtrate contains

a. Blood without blood cells and proteins

b. Plasma without sugar

c. Blood with proteins but without cells

d. Blood without urea

22. Kidney stones are produced due to deposition of uric acid and

a. silicates

b. minerals

c. calcium carbonate

d. calcium oxalate

23. Animal requiring minimum amount of water to produce urine are

a. ureotelic

b. ammonotelic

c. uricotelic

d. chemotelic

24. Aldosterone acts at the distal convoluted tubule and collecting duct resulting in the absorption of water through

a. Aquaphorins

b. spectrins

c. GLUT

d. Chloride channels

25. The hormone which helps in the reabsorption of water in kidney tubules is

a. cholecystokinin

b. angiotensin II

c. antidiuretic hormone

d. pancreozymin

26. Malpighian tubules remove excretory products from

a. mouth

b. oesophagus

c. haemolymph

d. alimentary canal.

27. Indentfiy the biological term Homeostasis, excretion, glomerulus,urea, glomerular filtration, ureters, urine, Bowman’s capsule, urinary system, reabsorption, micturition, osmosis, glomerular capillaries via efferent arteriole, proteins.

a. A liquid which gathers in the bladder. - Urine

b. Produced when blood is filtered in a Bowman’s capsule.

c. Temporary storage of urine.

d. A ball of inter twined capillaries. - glomerulus

e. A process that changes glomerular filtrate into urine. - excretion

f. Removal of unwanted substances from the body. - Bowman’s capsule

g. Each contains a glomerulus. - ureters

h. Carry urine from the kidneys to the bladder. - micturition

i. Contains urea and many useful substances. - Homeostasis

j. Bloods is filtered through its walls into the Bowman’s capsule. - urinary system

k. Scientific term for urination. - reabsorption

l. Regulation of water and dissolved substances in blood and tissue fluid. - proteins

m. Carry urine from the kidneys to the bladder.

n. Consists of the kidneys, ureters and bladder.

o. Removal of useful substances from glomerular filtrate.

p. The process by which water is transported in the proximal convoluted tubule.

q. Where has the blood in the capillaries surrounding the proximal convoluted tubule come from?

r. What solute the blood contains that are not present in the glomerular filtrate?

28. With regards to toxicity and the need for dilution in water, how different are ureotelic and uricotelic excretions? Give examples of animals that use these types of excretion?

29. Differentiate protonephridia from metanephridia

30. What is the nitrogenous waste produced by amphibian larvae and by the adult animal?

31. How is urea formed in the human body?

32. Differentiate cortical from medullary nephrons

33. What vessels carry blood to the kidneys? Is this blood arterial or venous?

34. Which vessels drain filtered blood from the kidneys?

35. What is tubular secretion? Name the substances secreted through the renal tubules

36. How are the kidneys involved in controlling blood volume? How is the volume of blood in the body related to arterial pressure?

37. Name the three main hormones are involved in the regulation of the renal function?

38. What is the function of antidiuretic hormone? Where is it produced and what stimuli increases or decreases its secretion?

39. What is the effect of aldosterone on kidneys and where is it produced?

40. What evolutionary hypothesis could explain the heart’s role in secreting a hormone that regulates renal function? What hormone is this?

Glossary

Atrial natriuretic peptide – is a polypeptide hormone released by atrial myocytes (muscle cells) from the granules of the atria of the heart in response to high blood pressure, hypervolemia and exercise. It is involved in the homeostatic control of body water and sodium.

Aquaporins – or water channels are formed by specific plasma membrane proteins in the tubular cells. These water channels of the proximal convoluted tubules are always open accounting for the high water permeability in this region. In contrast the water channels in the distal convoluted tubule are regulated by the hormone vasopressin accounting for the variable water re-absorption in that region.

Bowman’s capsule hydrostatic pressure – The pressure exerted by the fluid in the Bowman’s capsule. This pressure tends to push fluid out of Bowman’s capsule, opposes the filtration of fluid from the glomerulus into Bowman’s capsule.

Cortical nephrons – All nephrons originate in the cortex, but the glomeruli of the cortical nephrons lie in the outer layer of the cortex. Peri tubular capillaries do not form vasa recta.

Glomerular filtration – this is the first step in urine formation where 20% of the plasma that enters the glomerulus is filtered. The glomerular filtrate that comes out of the glomerulus into the Bowman’s capsule is the protein – free plasma.

Glomerular capillary pressure – It is the fluid pressure exerted by the blood within the glomerular capillaries.

Glomerulus – a tuft of capillaries that filters protein – free plasma into the tubular component

Juxtaglomerular apparatus – The ascending limb of Henle returns to the glomerular region of its own nephron, where it passes through the fork formed by the afferent and efferent arterioles. Both the tubular and vascular cells at this point are specialized to form juxtaglomerular apparatus that lie next to the glomerulus. (Juxta means “next to”).

Juxtamedullary nephrons – the glomeruli of the juxtaglomerular nephrons lie in the inner layer of cortex next to the medulla and the loops of Henle plunges through the entire depth of the medulla Concentrated urine is formed in these nephrons.

Filtration slits - The narrow slits between adjacent foot process that provides a pathway through which the fluid leaving the glomerular capillaries can enter the lumen of Bowman’s capsule.

Peritubular capillaries -supply the renal tissue, involved in exchanges with the fluid in the tubular region.

Podocytes – The glomerular membrane consists of octopus like cells called podocytes that entangles the glomerular tuft. Each podocyte bears many foot processes.

Vasa recta – (straight vessels) The peritubular capillaries of the juxtaglomerular nephrons forms vascular loops which run in close association with the loops of Henle.